Torque limiting wrenches have applications in various manufacturing environments where application of a consistent level of torque is needed. There are numerous reasons for desiring consistency in application of torque in a manufacturing process, such as, avoiding localized stressing of parts and assuring full tightening of fasteners.
It would be desirable for a manufacturing quality inspector to be able to visually check the level of torque applied to fasteners in a manufacturing environment. My previous patent, U.S. Pat. No. 4,393,734, herein incorporated by reference, discloses an invention which provides this inspection capability. This invention uses a pneumatic line to create pressure in a torque limiting wrench housing when the desired level of torque is reached. This pressure causes an ink-marking unit to slide toward the part and mark it for an inspector to see.
However, there are several problems with my previous invention. The attachment of a pneumatic line greatly limits the functional use of this tool in a manufacturing environment. It can be very difficult, cumbersome and prohibitively costly to provide pneumatic lines to certain locations in a manufacturing facility or assembly line. In addition, the attachment of these pneumatic lines limits the travel of the unit, i.e., the user is unable to walk around and perform work in areas where workspace is limited, areas where pneumatic lines are unavailable, or outside.
Another problem with my previous invention is that the use of metal-tipped ink-marking striking pins is inefficient. Not only is the ink mark difficult to see, but relatively large pneumatic line pressures are required in order to sufficiently force the striking pin against the part to mark the part.
Therefore, it would be desirable to develop a combined torque limiting and marking wrench which does not have the previously mentioned limitations.